This invention generally relates to a radio frequency transmitter which transmits a radio frequency signal when an abnormal state is occurs to an objective equipment included in a wireless security system, by monitoring the operational state thereof, and more particularly to a radio frequency transmitter which transmits the radio frequency signal for a given short period when the abnormal state is detected, by monitoring not only the abnormal state but also the drop of power supplied thereto.
In general, the wireless security system includes a plurality of the radio frequency transmitters for transmitting the radio frequency signal in the event that the abnormal state of the power with the radio frequency transmitters, and a central processing unit (CPU) for receiving the radio frequency transmitted from the radio frequency transmitters and controlling the objective equipment to which the abnormal state is occurred so as to operate in normal state.
Known radio frequency transmitter usually transmits the radio frequency signal carrying a specific code data, at the time that the abnormal state is detected. However, in the case that the power supply of battery loaded thereto is too low to operate the system, the transmitter can not detect the abnormal state or transmit the proper radio frequency because a function for monitoring the status of the battery is not prepared to the known system. Therefore, erroneous operation may occur frequently. Furthermore, the known transmitter is disadvantageous in that users must check the status of battery periodically and change the batteries in order to prevent the erroneous operation caused by lack of the power. A further disadvantage of the known transmitter is that the radio frequency signal resulted by detection of the abnormal state occurred to the objective equipment is continuously transmitted until a proper action is taken to the objective equipment, to recover from the abnormal state, which causes large power consumption.